It has been known for some time that optical fibers can be advantageously used to amplify, by means of stimulated Raman scattering, radiation guided through the fiber. Raman amplifiers and lasers appear to be excellent components for the use in transmission systems and especially in high-capacity photonic networks designed to provide various data-based broadband services.
Today's Raman amplifiers and lasers typically use silica, germano-silicate, or phospho-silicate based fibers. The Raman spectra of silica and germano-silica based fibers exhibit a single peak and the full bandwidth of Raman Stokes shift does not exceed 100 nm when pumped at 1.5 μm. Phospho-silicate fibers have a twin-peaked spectrum that shows one complementary localized shift at 300 nm when pumped at 1.5 μm.
Some proposals have been made so far for non high silica content based glass systems. EP 248 517 B1 discloses glass compositions for use in a Raman amplifier which contain GeO2 or SiO2 as glass-forming first component and a heavy metal oxide second component such as PbO, BiO1.5, SbO1.5, TlO0.5. These fibers have a silica-like bandwidth of Raman shift but are more efficient in terms of Raman gain coefficient.
The conference article “Ultra-wideband hybrid tellurite/silica fiber Raman amplifier” by H. Masuda, OFC 2002, ThB6, discloses tellurite-based glasses with a twin-peaked spectrum, which exhibit a large gain coefficient and bandwidth up to 170 nm when pumped at 1.5 μm.
It is an object of the present to provide a Raman-active glass composition for use in Raman amplifiers or lasers with improved flatness and bandwidth of Raman gain.